This invention relates to a light-weight, portable x-ray unit that can be utilized in a field environment. Portable x-ray units are primarily used in veterinary practices, but are useful in other emergency care situations where it is expeditious or more efficient to bring the x-ray unit to the patient than transport the patient to a facility having a standard medical x-ray machine.
It is expected that as the calibration and accuracy of portable units improve, widespread use of such units for the treatment of medical emergency patients will increase. Furthermore, portable units may have increased use in regions where hospitals or well equipped medical centers are unavailable. Such portable units are currently used for medical patients in nursing homes, where transport of the patient to a well-equipped facilities may be burdensome.
The existing inability to accurately calibrate a portable instrument for local conditions requires making multiple exposures at different settings to obtain useful diagnostic images. Not only does this entail unnecessary exposure, there is an uneconomical wastage of film, development chemicals and operator time. This greatly increases the cost of an x-ray examination.
Additionally, the extensive use of portable x-ray machines by veterinarians for examination of animals requires accuracy under a variety of operating conditions. Often use occurs in the field at the end of long extension cord for connection to a rural power source. Existing instruments are sensitive to low levels of source power and as a result may not operate at a consistent intensity. Also, a veterinarian must use a portable instrument on a variety of different animals where judgment of the operator is often critical given the diversity of animal species and size of animals, and the size of animal parts being examined. Frequently, the shortest exposure time on current equipment may be unduly prolonged for a very small animal or animal part, providing an uncorrectable over-exposure.
The design of current portable x-ray units is such that the life of the whole unit is usually limited by the life of the x-ray tube. The x-ray tube is customarily mounted together with a high tension transformer inside a sealed, oiled-filled tank unit. In most cases it is considered uneconomical to attempt any repairs on the sealed unit. Improvements in design that can reduce the number of exposures taken for each examination and reduce the stress on the x-ray tube and transformer during each exposure will naturally prolong the life of the tube and hence the equipment. Furthermore, an emulated, full-wave, rectified, d.c. power delivery to the emission tube of the invented unit reduces the extreme stress to the tube caused by conventional uncompensated, half-wave, rectified, power delivery to the lamp of existing, low-cost portable units.
The design of the invented portable x-ray unit prolongs the life of the unit and corrects the deficiencies of existing units. The improved design provides for accurate calibration within smaller increments, improving the safety of the device for use on humans, where greater care is required.